Phase change memory (PCM) technology such as multi-stack cross-point PCM is a promising alternative to other non-volatile (NV) memory technology, commonly known as non-volatile random access memory (NVRAM). In PCM memory cells, the threshold voltage window is defined as the difference between the set state threshold voltage (referred to as the SET VT) and reset state threshold voltage (referred to as the RESET VT) of the memory cell. It is desirable to have the threshold voltage window as large as possible. This may be accomplished by either lowering the SET VT or increasing the RESET VT.
PCM memory cells use a switch device, with a minimal on-state holding current (referred to as the holding current) that may be required to sustain the memory cell's on-state. Current passing through the memory cell may determine the level of SET VT. Providing a SET VT as low as possible may increase the threshold voltage window. In order to provide a SET VT as as low possible, a current passing through a memory cell at or near the holding current may be desired.